What is the most common site of ectopic pheochromocytoma (adrenal gland tumor)?

Most Common Site of Ectopic Pheochromocytoma

The para-aortic tissue, specifically the organ of Zuckerkandl near the origin of the inferior mesenteric artery or aortic bifurcation, is the most common site of ectopic pheochromocytoma. 1, 2, 3

Anatomical Distribution of Ectopic Pheochromocytomas

• Pheochromocytomas (PHEOs) can occur within the adrenal medulla or at extra-adrenal sites (paragangliomas or PGLs) 1
• Common locations of extra-adrenal paragangliomas include:
  • Para-aortic tissue/organ of Zuckerkandl (most common site) 1, 3, 4
  • Bladder 1
  • Heart/mediastinum 1, 4
  • Area between or above the aortic bifurcation 1

Organ of Zuckerkandl as Primary Site

• The organ of Zuckerkandl is a collection of chromaffin cells located near the origin of the inferior mesenteric artery or near the aortic bifurcation 3
• In a clinical series examining the distribution of pheochromocytomas, 53% of ectopic tumors were found in the organ of Zuckerkandl, making it the most common extra-adrenal site 4
• These para-aortic tumors can be locally invasive with major vessel involvement of the inferior vena cava, aorta, renal vein, and superior mesenteric artery/vein 1

Other Ectopic Sites

• Mediastinum: Less common site representing approximately 5% of ectopic pheochromocytomas 4
• Pelvis/bladder: Represents about 11% of ectopic cases 4
• Adjacent to adrenals: Approximately 26% of ectopic cases 4
• Neck: Rare location accounting for about 5% of ectopic cases 4

Clinical Significance of Location

• Para-aortic extra-adrenal retroperitoneal paragangliomas tend to have a higher incidence of clinically malignant behavior compared to other sites 1
• Surgical management of para-aortic tumors is challenging due to their proximity to major blood vessels and may require vascular reconstruction 1
• Open surgical approach is often recommended for para-aortic tumors to allow for manual assessment of vascular wall invasion and presence of lymph node disease 1

Diagnostic Considerations

• Imaging studies including CT, MRI, and functional imaging with 123I-MIBG scintigraphy are essential for localizing these tumors 2, 3
• Para-aortic tumors may present with symptoms of catecholamine excess including hypertension, headache, sweating, and palpitations 3

The evidence clearly indicates that the para-aortic tissue, particularly the organ of Zuckerkandl, is the most common site of ectopic pheochromocytoma, with studies showing that more than half of all ectopic cases occur in this location 4.